Water hammer dissipation in pneumatic slug tests
An edited version of this paper was published by AGU. Published 2007 American Geophysical Union. Doi:10.1029/2005WR004817
We model and measure the dissipation of water hammer induced by well casing and water elasticity with rapid valve opening at the start of a pneumatic slug test. The higher-frequency water hammer can obscure slower, aquifer-controlled, underdamped oscillations of the rigid water column, so a quantitative description of the elastic motion improves the ability of a slug test to calibrate the aquifer permeability k. Internal friction attenuates the water hammer, subject to a known headspace pressure at the air/water interface and equilibrium pressure at the top of the well screen. An analytical elastic solution is presented and matched to an existing rigid motion analysis, with matching predicated on k exceeding 7 × 10−14 m2 and appreciable water hammer dissipation during the first cycle of the slug test. The model is accurately calibrated with data from underdamped slug tests in a PVC monitoring well in the Plymouth-Carver Aquifer. The calibrated casing elasticity value suggests that effective lateral soil stress appreciably stiffened the casing.
David Ostendorf, Don J. DeGroot, and Philip J. Dunaj. "Water hammer dissipation in pneumatic slug tests" Water Resources Research 43 (2007).
Available at: http://works.bepress.com/david_ostendorf1/3